A study of phase transitions in cadmium perchlorate hexahydrate (Cd(ClO4)2.6H2O) by adiabatic calorimetry and infrared spectroscopy.
Abstract
A calorimetric study of Cd(ClO4)2.6H2O from 20 to 345 K shows 3 phase transformations, at 124.8,
238.45, and 271.62 K. IR spectra indicate that the low-temp. structure (below 124.8 K) contains 1
type of [Cd(OH2)6]2+, of symmetry C3 or C3v, and 2 types of ClO4-, both strongly distorted from
tetrahedral symmetry. There appears to be some disorder in this phase. The sharp transition at 124.8
K leads to major spectral changes, which indicate that H bonding is weakened, distortion of the
perchlorate ions is diminished, and [Cd(OH2)6]2+ symmetry is increased to D 3d. The more gradual
phase transition at 238.45 K involves no observable IR spectroscopic changes and may correspond to
an increase in ClO4- disorder. The very sharp transition at 271.6i K involves only very minor
changes in the IR spectra and may involve an increased disorder of the [Cd(OH2)6]2+ units.
Citation
Reproduced from White, Mary Anne, and Michael Falk. 1985. "A study of phase transitions in cadmium perchlorate hexahydrate (Cd(ClO4)2.6H2O) by adiabatic
calorimetry and infrared spectroscopy.." Journal of Chemical Physics 83(5): 2467-2474, with the permission of AIP Publishing.